I have loaded it to the plugin folder, but i cant find it at the admin -->plugins -->all

You did install it correctly? Note that you need to upload the file and the folder, not the main folder from the repo.

yes,
gslideshow.php
and the folder gslideshow are in the folder plugins

Just to be sure ;-)

gslideshow (folder)

Just to be sure ;-)

gslideshow (main folder) contains:
gslideshow (folder) => goes in plugins folder
gslideshow.php (file) => goes in plugins folder

Just to be sure ;-)

[list]
[*]
gslideshow (main folder) => does NOT go in the plugins folder

gslideshow (subfolder) => goes in plugins folder
[*]gslideshow.php (file) => goes in plugins folder
[/list]

And in your theme options you have to un-check [i]Use Colorbox Slideshow[/i]

yes,all files are uploaded to the plugin folder.

and it is not shown in the admin --> plugins

Again ;-)

NOT the main folder, ONLY the folder and file within.